| 摘要 |
<p>The invention concerns monitoring large structures to detect defects, e.g. cracks. An electric current is impressed on a steel structure (31, 32) equipped with contact points (41-45) between which are measured voltage drops caused by the impressed current. A relatively large number of fixed contact points are used all over the area which is to be monitored. The voltage drops are measured between selected pairs of contact points and these voltage drops are compared with corresponding voltage drops having been measured previously in the same manner when the structure was in an initial condition, preferably without any defects. Such monitoring is mainly applicable on oil drilling rigs and petroleum production platforms for exploitation of oil and gas fields offshore, where it is important that the monitoring can be performed by means of robust and simple devices resistant to the prevailing arduous enviroment.</p> |
